Oven thermostat



v.June 10, 1930. E. E. LEDBr-:TTER

ovEN THERMOSTAT 5 sheets-snaai 1 Filed May 9,1 1927 June 1o, 1930.

E. E. LEDBETTER l OVEN THERMOSTAT I5 Sheets-Sheet 2 Filed May 9, 1927 @manto/c [2722 err/ET @die t er yrmmj ,www

E. E. LEDBETTER June l0, 1930.

OVEN THERMOSTAT Filed May 9, 1927 3 Sheets-Sheet 3 nwuboz abbot/wmf@ MX bv 2 Q l i Q uw /y www Patented June 1o, y1930 UNITED STATES PATENT OFFICE ELMER E. LEDBETTER, 0F DETROIT, MICHIGAN, ASSIGNOR-TO EVER HOT HEATER COM- PANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN OVEN THERMOSTAT Application led Hay 9,

The invention relates to thermostats and more particularly to that type of thermostat adapted for use in regulating the temperature of ovens and the like. I

One of the principal objects of the 1nvention is to obtain a valve mechanism d1- rectly actuated by the longitudinal eXpansion and contraction of the thermostat without levers or other devices for obtaining mechanical advantage, said valve mechanism being provided with means for ad]u st ing the same to the desired temperature with extreme accuracy, the arrangement belng such that the device may be set to any predetermined temperature within the normal range of oven temperatures and will operate to maintain said temperature within narrow limits of uctuation.

Another object is to provide rotatably adjustable means for setting the thermostatically actuated valve, said means being operable by substantially a full` revolution thereof in order to regulate the temperature between the upper and lower limits of the normal range of oven temperatures.

Another object is to provide a thermostat in which the valve mechanism is arranged outside of the oven walls, and the pipe connections leading to the burner are attached to the device within the oven Walls.

A further object is to provide a device, which when mounted on the oven, requires only a single aperture in the oven wall, the pipe connections being concealed within the oven and attached to the portion of the device within thev oven.

These and other objects are attained by my invention, several embodiments of which are illustrated in the accompanying drawings, wherein- Figure 1 is a longitudinal section through the thermostat; y

Figure 2 is an elevation of the regulating end thereof;

Figure 3 is a transverse section on the line 3 3 of Figure 1;

Figure 4 is a similar section on the line 4 4 of Figure 1;/

Figure 5 is a section on the line 5-5 of Figure 1;

1927. Serial No. 190,023.

Figure 6 is a side elevation of the rotatable Referring first to the embodiment of the invention illustrated in Figures 1 to 7, the thermostatic device comprises a fixed casing or body 1 arranged within the oven, a valve mechanism 2 extending from said body to the outside of the oven and a thermostat 3 extending from the body 1 in the opposite direction and locatedl within the oven.

The thermostat 3 comprises two elements having different coeiicients of expansion, the outer tubular member 4 which is permanent-ly secured to the body 1 at 5, and the inner rod 6 arranged within the tube 4 and extending vthrough a longitudinal aperture in the body 1 into the rotatable housing y2. 7 is a cap permanently secured to the tube 4 and provided with internal threads 8 for adjustably securing the inner rod 6. Any suitable materials may be used for the parts of the thermostat, butin the preferred construction the outer tube 4 is of copper, the inner rod 6 is of steel and the body 1 is of brass. These materials are practical from a production standpoint, and there' is a suicient differential in the coeiicients of expansion of the steel on the casing an annular passageway 11 which leads into an enlarged chamber 12. The portionof the casing or body containing the chamber 12 is of substantlally circular cross section, and is arranged eccentrically to the tube 9 so that the greater portion of the chamber is'y arranged below the tube. At the lower side of this eccentric portion of the body there are provided two threaded apertures, 13 and 14,the former constituting the inlet aperture and extending through the tube 9 into the annular passageway 10, and the latter constituting an outlet port and extending into the passageway 15. The passageway 15 extends longitudinally of the body into the chamber 12. The threaded apertures 13 and 14 are preferably arranged at an angle of 90 so that the inlet and outlet pipes 16 and 17, which are connected thereto, will extend downwardly within the oven.

. The valve mechanism 2 comprises a rotatable valve seat 20 to which is 'secured a valve housing cap 21 forming the valve chamber 22. The valve seat' 20 is adjustably secured to the body 1 by the threaded extension 23 which surrounds the tube 9 forming a continuation of the passageway 11. 24 is a disk valve longitudinally slidable on the tube 9 and provided with an annular knife-edge portion 25 for engaging the valve seat 20. The valve 24 is at all times urged toward its seat by the spring 26 between the valve and the housing cap 21. The valve 24 has a central head portion 27 surrounding the reduced end of the thermostatic rod and engageable with the annular shoulder 28 of the latter. The head is provided with radial apertures 49 extending through the side walls thereof ail'ording communication between the passageway 10 and the valve chamber 22. The reduced end of the rod 6 is axially movable within an aperturedvboss 29 on the housing cap and is provided with a slotted end 30 for engaging a pin 31 carried by said boss.

or rotating the housing 21 there is provided a hand wheel '32 clamped to the housing by a cap 33 and screw- 34. The ,hand wheel is held from rotation relative to the housing by the heads of the screws 35 which engage recesses in the hand wheel. The screws 35 also serve to secure the valve seat and the housing cap together. The temperature calibrations are marked upon the outer circumference of the rotatable housing and i the reading is indicated by means of a pointer 36 extending from a cover plate 37 secured "to the body 1. In the illustrated construction the calibrated scale is marked upon a strip 38 bent into annular form and held in position by clamping the same between the valve seat 20, and the hand wheel 32. Each of these members is provided with an annular groove 39 and 40 respectively, for

receiving the edges of the strip and the ends of the strip are arranged within an H block 40. With this arrangement the calibrated strip together with the H block may be rotatably adjusted on the housing to the desired position and afterwards clamped by the hand wheel 32. The H block 40 is preferably extended suiliciently to engage the pointer 36, thus constituting a stop for preventing more than one revolution of the housing;

It is usual to provide a by-pass around the thermostatic valve so that a small quantity of gas sufficient to maintain a pilot light will at all times be delivered irrespective of the setting of the valve. In my construction the b -pass is arranged in the body 1 between t e inlet passageway 10 and the outlet passageway 15. A radial bore 46 is drilled through the body 1 and a needle valve 47 is inserted therein, being adjustable by the rotation of the threaded head 48. The tube 9 has drilled therein an orifice in alignment with theradial bore and of such size as to cooperate with the end of the needle valve to produce the proper regulation of the gas.

The thermostatic device is mounted on the ovenby inserting the body 1 through an aperture 43 in the outside oven wall 42, the

body being suitably secured within the oven.

In the usual construction of ovens an inner wall 44 is provided, and also an inner-lining 45. My construction is ada ted to be inserted within the oven so t at the casing or body 1 is located between the outer oven wall and the inner-lining. The conduits 16 and 17 leading from the body may therefore be carried downward inside of the outer oven wall and the conduit 17 may be connected to the oven burner without being brought outside of the oven walls. The other conduit 16 ma be connected to the supply line at a suita le point less conspicu ous than the location of the thermostat. The eccentric relation of the main ortion of the body 1 with reference to the t ermostat enables the placing of the device close to the top of the oven so thatl the thermostat may extend inwardly in the channelv formed in the top of the oven inner-lining in the usual l III 3.111161,

the range of oven temperatures.

As heretofore mentioned, one.of the principal advantages of the construction is that it permits very accurate regulation of the temperature by the provision of a directly actuated valve connected to the thermostat. With such a' construction the maximum movement of the valve due to the differential longitudinal expansion of the thermostatic elements is comparatively small, and yet it is necessary to provide means for adjusting the thermostatic elements relative to each other so that the valve will be adjusted to maintain any desired temperature within It is evident that if the operating handle turns through substantially a full revolution between the upper' and lower temperatures, it must be adjustably connected to the thermostat to impart only a minute axial movement thereto for each position of rotative adjustment. In the device illustrated in Figure 1 this is accomplished by means of differential threads. Thus the threads 23 are of slightly different pitch than the threads 8 so that upon rotation of the hand wheel, while both the housing 21 and the thermostatic rod 6 are axially advanced relative to the body,

the relative movement between the valve seat 20 and the valve 24 is only a fraction of the total movement.v This enables the use of standard threaded connections for both the rotatable housing and the thermo-v during a `complete revolution of the housing.

There are other methods of obtaining the fine adjustment between the valve and valve seat, and in Figure 10 I .have illustrated a modified construction which accomplishes the same results in a different manner. In this construction the valve seat 20a is nonadjustably secured to the body 1 and is preferably made' integral therewith. The valve housing 21al by'being secured to the valve seat 20a is therefore non-adjustably mounted with respect to the body 1 and serves merely to enclose the valve 24 in a position outside of the oven wall 42. The thermostat is similar in construction to the one previously described, except that the cap 22a instead of being permanently secured to the outer tube 3 is adjustably secured thereto by the .threads 49. The steel rod 6 is also adjustably secured to the cap 22a by the threads 8 mechanism, and having secured at its outer.

end a suitable hand wheel 52. The periphery of the hand wheel may be provided with calibrations which cooperate with a fixed pointer 53 secured to the oven Wall.

Figures 8 and 9 illustrate another modified construction wherein the adjustment of the valve is obtained by the use of a single threaded connection. In this construction the valve housing 21a is similar to that shown in Figure 10 and is non-adjustably secured to the body 1. The thermostat is provided at its outer end with a cap 54 permanently secured to the outer tube 3 in the same manner as illustrated in Figure 1, and has an extension 55 interiorly threaded at 56 for4 play or lost motion. .The preferred. construction of the threaded connection is obtained in the following manner.

The outer end ofthe extension 55 is longitudinally slotted in several places as indicated at 58, and the segments 59 produced by the slots are compressed inwardly by means of a compression nut 60. This nut -has tapered threads 61 which engage corresponding tapered threads 62 on the exterior of the extension 55. In the manufacture ofthe cap 54 and the rod 6 these parts are assembled in threaded engagement, and the compressionnut 60 is placed in position on the extension 55 and rotated until the segments 59 are forced into firm frictional engagement with the threaded end of the rod 6. The rod 6 is then rotated, rst in one direction and then the other direction, to lap the threads 56 and 57 and remove any inaccuracies in the threads. During the lapping process the cap 60 is periodically advanced on the tubular extension 55 to take its is only one complete revolution while the two parts are connected together by a plurality of thread convolutions, it will be read! ily apparent that the method outlined above will insure th`e formation of a very accurate adjustment means for the thermostat. 1f any lost .motion develops in the threaded connection after the thermostat is in commercial use this may be eliminated by further advancing the compression nut 60 on the cap, thereby increasing the compression of the segments 59. It is preferable that the inner end of the nut 60 be threaded onto the extension 55 sufficiently so as to entirely cover the slots 58 and also cover a portion of the unslotted cap, so that a gastight joint will be made.

For adjustably rotating the rod 6 there is provided an adjusting wheel 63, preferably mounted on an extension 64 of the rod 6 which projects through the valve housing cap 21a. The extension 64 is caused to have a tight seal with the housing cap 21a in any suitable manner, such for instance as providing the packing 65 and the packing nut 66. The. hand Wheel 63 is keyed or otherwise secured to the extension 64 and is preferably provided with an annular flange 67 surrounding the housing cap 21a. The calibrations are marked upon the outer periph# ery of the flange 67, and the setting of the thermostat is indicated by a pointer 68 secured to the valve seat 2Oa and extending over the flange 67.

In all of the constructions described' above, I have illustrated thermostatic devices which are capable of being used as oven regulators and will accurately control the temperature of the oven within the usual range of oven temperatures, which is ordinarily from 250 degrees to 550 degrees F. The constructions are all adapted to be mounted onA an oven without requiring any external piping, since the inlet and outlet gas conduits are connected to the portion of the fixed casing arranged within the oven walls. The valve mechanism and the regulating mechanism is in each case arranged outside of the ovenwalls, thus avoiding the excessive heat. The constructions are also such that the valve mechanism is readily accessible and can be removed without affecting the calibration of the thermostat.

As heretofore mentioned, the preferred materials for the thermostat are copper or brass for the more eXpansible element and steel for the less eXpansible element. It has been found that ordinary steel is well suited for the rod 6, since its coefficient of expansion is substantially constant throughout the range of oven temperatures. In the modification illustrated in Figure 8 it may be desirable to substitute stainless steel for ordinary steel in order to insure that no Vcorrosion takes place in the threads 57 where extreme accuracy must always be maintained to insure the accuracy of the thermostat.

What I claim as my invention is:

1. An oven regulator comprising a valve seat, a valve cooperating therewith, an eX- pansible tube having one end connected to said valve seat, a less expansible rod connected to the other end of said tube, said rod being operably connected to said valve to directly Vactuate the latter by dierential longitudinal movement of said tube and rod, and rotatably adjustable means operable through substantially a full revolution for setting said valve relative to said seat to correspond to the normal range of oven temperatures, said means including two sets of threads of diierent pitch adapted for simultaneous adjustment.

2. An oven regulator comprising a fixed casing, having inlet and outlet ports arranged within the outside wall of the oven, a valve mechanism arranged outside of said wall, thermostatic means for operating said valve mechanism and means outside of said wall for setting said valve mechanism to operate at varying temperatures.

3. An oven regulator comprising a fixed casing within the outside wall of the oven, a valve housing outside of said wall, inlet and outlet conduits connected to said casing within the said outside wall, a valve within said valve housing, separate passageway/s4 leading from said inlet and outlet conduits to` said valve housing on opposite sides of -said valve, a thermostat operatively connected to said valve and means for adjustably setting said thermostat to close said valve at varying temperatures.

4. An oven regulator comprising a fixed casing, having inlet and outlet ports therein, a valve housing, a valve within said housing, a tubular member connecting said valve housing and said casing, a second tubular member within said first tubular member, forming between the same a passageway connecting one of said ports with the valve `housing on one side of said valve, the interior of said second tubular member forming a passageway connecting the other port with the valve housing on the other side of said valve.

5. An oven -regulator comprising a casing within the outside wall of the oven, having inlet and outlet ports therein, a valve housing outside of said oven, a tubular member extending through the oven wall connecting said casing and said valve housing, a 1second ltubular member extending from said casing through said first tubular member to saidvvalve housing, a disk valve within said housing sleeved on said secondtubular member and a thermostat for longitudinally adjusting said valve relative to said housing.

6. An oven regulator comprising a hollow casing within the outside wall of the oven, having a pair of fuel ports therein, an expansible thermostatic tube secured to and projecting from' one end of said casing, a second tube projecting from the opposite end of said casing, a valve housing carried by said second tube, a thermostatic member having a smaller coefiicient of expansion than said thermostatic tube, said thermostatic member having one end thereof secured to said expansible tube and having the other end extending through said casino' to said valve housing, a third tube projectlng from said casing into said valve housing forming separate passageways interiorly and exteriorly thereof, communicating respectively with said fuel ports, a disk valve within said housing slidable on said third tube and operatively connected to said thermostatic member.

7. An oven regulator comprising a hollow casing having a pair of fuel ports therein, a tubular thermostatic member secured to and projecting from one end of said casing, a second tube projecting from the opposite end of said casin a valve housing carried by said second tue, a third tube projecting from said casing into said valve housing forming longitudinally extending passageways interiorly and exteriorly thereof, a disk valve within said housing slidable on said third tube, a thermostatic rod o eratively connected to said valve and a just- -ably threadedly connected to said thermostatic tube and rotatably adjustable means operable through substantially a full revolution for longitudinally adjusting the thermostatic rod with respect to said thermostatic tube.

' 8. In an oven regulator the combination of a fixed casing adapted to be secured within the outside wall of an oven, and having inlet and outlet fuel ports adapted to be connected to a fuel line within the oven, a valve housing, a tubular member connecting said casing and valve housing, a valve within said housing and means for forming two separate passageways within said tube leading respectively to said valve housing on opposite sides of said valve.

9. An oven regulator comprising a hollow body adapted to be secured within the outside wall of the oven, an expansible tube projecting from said body, a less expansible rod connected to said tube and lextending through said body, a valve housing projecting oppositely from said tube and provided with a tubular extension connecting the same to said hollow body, a valve within said housing operatively connected to said thermostatic rod and means for forming two separate passageways through said tubular extension into said valve` housing, said passageways communicating respectively on opposite sldes of said valve.

10. An oven regulator comprising a hollow casing, a valve housing connected to and longitudinally spaced-from said casing,

`a gas conduit within said hollow casing extending toward said valve housing, a disk valve longitudinallymovable in said housing, said valve having a passageway therethrough and means connecting said gas conduit and valve for maintaimng a passa eway between the gas conduit and t e va ve housin duringthe movement of said valve.

11. n oven regulator comprising a valve housing having an annular seat, a disk valve axially movable within said housing and provided with an aperture therethrough, a gas conduit projecting from said housing and communicating therewith between said seat and one side of said valve, a second gas conduit connected to said valve to' maintain communication through said aperture to the portion of the valve housing on the opposite side of the valve, and a thermostatically operated member for axially moving said valve relative to said seat.

12. An oven regulator comprising a valve housing having an annular seat, a disk valve axially movable within said housing and provided with an a rture therethrough, a gas conduit projectmg from said housing and communicating therewith between said seat and one side of said va1ve,a second as Iconduit telescopically engaging said va ve l casing having inlet and outlet ports arranged within the outside wall of the oven, a valve mechanism arranged outside of said wall, thermostatic means for yoperating said valve mechanism, said thermostatic means extendin through the portion of the casing having tie inlet and outlet ports therein, and means outside of the outside walls of the oven operable through substantially a" full revolution for adjustably setting said valve mechanism to operate at varying temperature's between the upper and lower limits of the normal rangeof oven temperatures.

14. An oven regulator comprisin a. fixed casing within an outside wall of t e oven,- a valve housing outside of said lwall, inlet and outlet conduits connected to said casing within said outside wall, a valve within said valve housing, separate passageways leading. from said inlet and outlet conduits to said valve housing onopposite sides of said valve, a thermostat operatively connected to said valve comprising two longitudinally properties, saidthermostat being arranged in the portion ofsaid fixed casing having the inlet and outlet ports therein, and means operable through substantially a full revolution for adjustably setting said thermoture, an operating handle outside of said oven wall rotatable between limiting positions arranged substantially a full revolution apart, threaded means operable b s'aid handle for variably adjusting the settlng of said valve relative to said seat and means cooperating with said threaded means to cause said valve to seat at the upper and lower limits of the normal range of oven temperatures corresponding respectively to the aforesaid opposite limiting positions of rotative adjustment of said handle when the oven temperature is at or above the temperature at which said handle is set.

16. An oven regulatorcomprising a valve housing having a valve seat, a valve within said housing, an expansible non-ferrousmember extending from said valve housing, a less expansible ferrous member having one end connected to said expansible member and the other end operatively connected to said valve, resilient means cooperating with said operative connection to-move the valve relative to said valve seat upon change in temperature, an operating handle outside of said oven wall rotatable between limiting positions arranged substantially a full revolution apart, threaded means operable by said handle for variably adjusting the setting of said valve relative to said seat and means cooperating with said threaded means to cause said valve to seat at the upper and lower limits of the normal range of oven temperatures corresponding respectively to the aforesaid opposite limiting ositions of rotative adjustment of said hand e when the oven temperature is at or above the temperature at which said handle is set.

17. An oven regulator comprising a valve housing having a valve seat, a valve within said housing, an expansible bronze member extending from said valve housing, a less expansible steel member having one end connected to said `expansible member and the other end operatively connected to said valve, resilient means cooperating with said operative connection to movethe valve relaperatureat which said handle is set.

418. An oven regulator comprising a valve housing having a valve seat, a valve within said' housing, a bronze member extending from said valve housing, a steel member connected between said bronze member and said valve, resilient means-cooperating with said steel member to move said valve relative to said valve seat upon change in temperature, an operating handle rotatable between limiting positions substantially a full revolution apart and dierentially movable threaded means rotatable by said operating handle,

said threaded means being interposed between said valve housing and said valve.

In testimony whereof I affix my signature.

ELMER E. LEDBETTER. 

